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Chapter 22: Problem 34

Show how to convert toluene to (a) 2,4-dinitrobenzoic acid and (b) 3,5 -dinitrobenzoic acid.

Short Answer

Expert verified
Question: Outline the step-by-step process to convert toluene to (a) 2,4-dinitrobenzoic acid and (b) 3,5-dinitrobenzoic acid. Answer: (a) To convert toluene to 2,4-dinitrobenzoic acid: 1. Perform nitration of toluene using a mixture of nitric acid (HNO3) and sulfuric acid (H2SO4) to form 2,4-dinitrotoluene. 2. Oxidize the methyl group in 2,4-dinitrotoluene using potassium permanganate (KMnO4) in an alkaline medium to form 2,4-dinitrobenzoic acid. (b) To convert toluene to 3,5-dinitrobenzoic acid: 1. Perform halogenation of toluene using N-bromosuccinimide (NBS) and benzoyl peroxide (BPO) to form m-bromotoluene. 2. Nitrate the m-bromotoluene using a mixture of nitric acid (HNO3) and sulfuric acid (H2SO4) to form 3-bromo-5-nitrotoluene. 3. Oxidize the methyl group in 3-bromo-5-nitrotoluene using potassium permanganate (KMnO4) in an alkaline medium to form 3-bromo-5-nitrobenzoic acid. 4. Perform a second nitration on 3-bromo-5-nitrobenzoic acid using a mixture of nitric acid (HNO3) and sulfuric acid (H2SO4) to form 3,5-dinitrobenzoic acid.

Step by step solution

01

Nitration of Toluene

In the first step, we will perform nitration of toluene to form 2,4-dinitrotoluene. To do this, we will need a mixture of nitric acid (HNO3) and sulfuric acid (H2SO4). The reaction proceeds as: Toluene + 2 HNO3 -> 2,4-dinitrotoluene + 2 H2O
02

Oxidation of Methyl group to Carboxylic Acid Group

Next, we will oxidize the methyl group in 2,4-dinitrotoluene to form the carboxylic acid group in 2,4-dinitrobenzoic acid. This is achieved using an oxidizing agent like potassium permanganate (KMnO4) in an alkaline medium, followed by an acidic work-up. The reaction is as follows: 2,4-dinitrotoluene + KMnO4 + H2O -> 2,4-dinitrobenzoic acid + MnO2 + KOH (b) Conversion of toluene to 3,5-dinitrobenzoic acid
03

Halogenation of Toluene

To obtain 3,5-dinitrobenzoic acid, it is necessary to introduce a directing group in the meta position. This can be done through halogenation of toluene. We will use N-bromosuccinimide (NBS) as the brominating agent with benzoyl peroxide (BPO) as a radical initiator. The reaction proceeds as: Toluene + NBS + BPO -> m-Bromotoluene
04

Nitration of m-Bromotoluene

Next, we nitrate the m-bromotoluene using a mixture of nitric acid (HNO3) and sulfuric acid (H2SO4). The reaction proceeds as: m-Bromotoluene + HNO3 -> 3-bromo-5-nitrotoluene + H2O
05

Oxidation of Methyl group to Carboxylic Acid Group

Now, we oxidize the methyl group in 3-bromo-5-nitrotoluene to form the carboxylic acid group in 3-bromo-5-nitrobenzoic acid, using potassium permanganate (KMnO4) in an alkaline medium, followed by an acidic work-up. The reaction is as follows: 3-bromo-5-nitrotoluene + KMnO4 + H2O -> 3-bromo-5-nitrobenzoic acid + MnO2 + KOH
06

Nitration of 3-bromo-5-nitrobenzoic acid

Finally, we perform a second nitration on 3-bromo-5-nitrobenzoic acid to introduce the second nitro group at the desired position. For this, we again use a mixture of nitric acid (HNO3) and sulfuric acid (H2SO4). The reaction proceeds as: 3-bromo-5-nitrobenzoic acid + HNO3 -> 3,5-dinitrobenzoic acid + HBr + H2O

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